| dish: soup|
In a kettle cook the onion and parsley in the butter and the oil over moderately low heat, stirring, until it is softened, add the squash and enough water to just cover, and cook the mixture, covered, over moderately low heat for 20 to 30 minutes, or until the squash is tender. Add the broth and simmer the mixture, uncovered, for 15 minutes. In a blender or food processor purée the mixture in batches. The soup may be made 1 day in advance and kept covered and chilled.
Ladle the soup into 8 bowls and garnish each serving with a sprig of parsley.